Coarse-grained mean field simulations of a triblock copolymer system. The effect of flexibility on the micellization behavior

2019 ◽  
Author(s):  
Maria Pantelidou ◽  
Allan D. Mackie
Keyword(s):  
Triblock Copolymer ◽  
Mean Field ◽  
Coarse Grained ◽  
Micellization Behavior

Grand-Reaction Method for Simulations of Ionization Equilibria and Ion Partitioning in a Broad Range of pH and Ionic Strength

2019 ◽  
Author(s):  
Jonas Landsgesell ◽  
Oleg Rud ◽  
Pascal Hebbeker ◽  
Raju Lunkad ◽  
Peter Košovan ◽  
...  
Keyword(s):  
Mean Field ◽  
Coarse Grained ◽  
Reactive System ◽  
Acid Base ◽  
Buffer Solution ◽  
Reaction Method ◽  
Ionization Equilibria ◽  
Coarse Grained Simulations ◽  
Ph Range ◽  
Weak Polyelectrolytes

We introduce the grand-reaction method for coarse-grained simulations of acid-base equilibria in a system coupled to a reservoir at a given pH and concentration of added salt. It can be viewed as an extension of the constant-pH method and the reaction ensemble, combining explicit simulations of reactions within the system, and grand-canonical exchange of particles with the reservoir. Unlike the previously introduced methods, the grand-reaction method is applicable to acid-base equilibria in the whole pH range because it avoids known artifacts. However, the method is more general, and can be used for simulations of any reactive system coupled to a reservoir of a known composition. To demonstrate the advantages of the grand-reaction method, we simulated a model system: A solution of weak polyelectrolytes in equilibrium with a buffer solution. By carefully accounting for the exchange of all constituents, the method ensures that all chemical potentials are equal in the system and in the multi-component reservoir. Thus, the grand-reaction method is able to predict non-monotonic swelling of weak polyelectrolytes as a function of pH, that has been known from mean-field predictions and from experiments but has never been observed in coarse-grained simulations. Finally, we outline possible extensions and further generalizations of the method, and provide a set of guidelines to enable safe usage of the method by a broad community of users.<br><br>

scholarly journals Mean-Field Models for EEG/MEG: From Oscillations to Waves

2021 ◽  
Author(s):  
Áine Byrne ◽  
James Ross ◽  
Rachel Nicks ◽  
Stephen Coombes
Keyword(s):  
Gap Junction ◽  
Large Scale ◽  
Mean Field ◽  
Coarse Grained ◽  
Neural Mass Model ◽  
Neuron Network ◽  
Mass Model ◽  
Mean Field Model ◽  
Neural Mass ◽  
The Rich

AbstractNeural mass models have been used since the 1970s to model the coarse-grained activity of large populations of neurons. They have proven especially fruitful for understanding brain rhythms. However, although motivated by neurobiological considerations they are phenomenological in nature, and cannot hope to recreate some of the rich repertoire of responses seen in real neuronal tissue. Here we consider a simple spiking neuron network model that has recently been shown to admit an exact mean-field description for both synaptic and gap-junction interactions. The mean-field model takes a similar form to a standard neural mass model, with an additional dynamical equation to describe the evolution of within-population synchrony. As well as reviewing the origins of this next generation mass model we discuss its extension to describe an idealised spatially extended planar cortex. To emphasise the usefulness of this model for EEG/MEG modelling we show how it can be used to uncover the role of local gap-junction coupling in shaping large scale synaptic waves.

scholarly journals On the three-dimensional spatial correlations of curved dislocation systems

2021 ◽  
Vol 5 (1) ◽  
Author(s):  
Joseph Pierre Anderson ◽  
Anter El-Azab
Keyword(s):  
Correlation Function ◽  
Slip System ◽  
Correlation Functions ◽  
Mean Field ◽  
Coarse Graining ◽  
Dislocation Dynamics ◽  
Coarse Grained ◽  
Spatial Correlation Function ◽  
Line System ◽  
Dislocation Densities

AbstractCoarse-grained descriptions of dislocation motion in crystalline metals inherently represent a loss of information regarding dislocation-dislocation interactions. In the present work, we consider a coarse-graining framework capable of re-capturing these interactions by means of the dislocation-dislocation correlation functions. The framework depends on a convolution length to define slip-system-specific dislocation densities. Following a statistical definition of this coarse-graining process, we define a spatial correlation function which will allow the arrangement of the discrete line system at two points—and thus the strength of their interactions at short range—to be recaptured into a mean field description of dislocation dynamics. Through a statistical homogeneity argument, we present a method of evaluating this correlation function from discrete dislocation dynamics simulations. Finally, results of this evaluation are shown in the form of the correlation of dislocation densities on the same slip-system. These correlation functions are seen to depend weakly on plastic strain, and in turn, the dislocation density, but are seen to depend strongly on the convolution length. Implications of these correlation functions in regard to continuum dislocation dynamics as well as future directions of investigation are also discussed.

Mesoscopic study of the ternary phase diagram of the PS–PB–PtBMA triblock copolymer: modification of the phase structure by the composition effect

Soft Matter ◽  
2018 ◽  
Vol 14 (4) ◽  
pp. 508-520 ◽  
Author(s):  
David Alfredo González-Pizarro ◽  
Cesar Soto-Figueroa ◽  
María del Rosario Rodríguez-Hidalgo ◽  
Luis Vicente
Keyword(s):  
Phase Diagram ◽  
Triblock Copolymer ◽  
Ternary Phase ◽  
Ternary Phase Diagram ◽  
Dissipative Particle Dynamics ◽  
Particle Dynamics ◽  
Coarse Grained ◽  
Butyl Methacrylate ◽  
Composition Effect ◽  
Ordered Nanostructures

We explored in detail the ordered nanostructures and the ternary phase diagram of the polystyrene–polybutadiene–poly(tert-butyl methacrylate) (PS–PB–PtBMA) triblock copolymer via dissipative particle dynamics (DPD) simulations and coarse-grained models.

scholarly journals Hydrophobic droplets in amphiphilic bilayers: a coarse-grained mean-field theory study

Soft Matter ◽  
2012 ◽  
Vol 8 (12) ◽  
pp. 3308 ◽  
Author(s):  
Martin J. Greenall ◽  
Carlos M. Marques
Keyword(s):  
Field Theory ◽  
Mean Field Theory ◽  
Mean Field ◽  
Coarse Grained

Mesoscale Simulation of Morphology in Hydrated Perfluorosulfonic Acid Membranes

2005 ◽  
Vol 885 ◽  
Author(s):  
James T. Wescott ◽  
Yue Qi ◽  
Lalitha Subramanian ◽  
T. Weston Capehart
Keyword(s):  
Mesoscale Model ◽  
Random Network ◽  
Mean Field Theory ◽  
Mean Field ◽  
Domain Size ◽  
Proton Exchange ◽  
Coarse Grained ◽  
Perfluorosulfonic Acid ◽  
Perfluorosulfonic Acid Membranes ◽  
Hydrophilic Domain

ABSTRACTCurrent fuel cell proton exchange membranes (PEM) rely on a random network of conducting hydrophilic domains to transport protons across the membrane. Despite extensive investigation, details of the structure of the hydrophilic domains in these membranes remain unresolved. In this study a dynamic self-consistent mean field theory has been applied to obtain the morphologies of hydrated Perfluorosulfonic Acid (PFSA) (equivalent weight of 1100) as a model for Nafion® at several water contents. A coarse-grained mesoscale model was developed by dividing the system into three components: backbone, side chain, and water. The interaction parameters for this model were generated using classical molecular dynamics. The simulated morphology shows phase separated micelles filled with water, surrounded by side chains containing sulfonic groups, and embedded in the fluorocarbon matrix. For λ<6 (λ gives the ratio of water molecules to sulfonic groups), the isolated domains obtained from simulation are nearly spherical with a domain size smaller than that fitted to experimental SANS data. For λ>8; the domains deform into elliptical and barbell shapes as they merge. The simulated morphology, hydrophilic domain size and shape are generally consistent with some experimental observations.

scholarly journals PROJECTED SO(5) HAMILTONIAN FOR CUPRATES AND ITS APPLICATIONS

2001 ◽  
Vol 15 (19n20) ◽  
pp. 2509-2518 ◽  
Author(s):  
ASSA AUERBACH ◽  
EHUD ALTMAN
Keyword(s):  
Hole Concentration ◽  
Mean Field ◽  
Resonance Energy ◽  
Differential Resistance ◽  
Field Approximation ◽  
Quantum Spin ◽  
Coarse Grained ◽  
Mean Field Approximation ◽  
Antiferromagnetic Resonance ◽  
Experimental Phase Diagram

The projected SO(5) (pSO(5)) Hamiltonian incorporates the quantum spin and superconducting fluctuations of underdoped cuprates in terms of four bosons moving on a coarse grained lattice. A simple mean field approximation can explain some key features of the experimental phase diagram: (i) The Mott transition between antiferromagnet and superconductor, (ii) the increase of T c and superfluid stiffness with hole concentration x and (iii) the increase of antiferromagnetic resonance energy as [Formula: see text] in the superconducting phase. We apply this theory to explain the "two gaps" problem in underdoped cuprate SNS junctions. In particular we explain the sharp subgap Andreev peaks of the differential resistance, as signatures of the antiferromagnetic resonance (the magnon mass gap). A critical test of this theory is proposed. The tunneling charge, as measured by shot noise, should change by increments of ΔQ=2e at the Andreev peaks, rather than by ΔQ=e as in conventional superconductors.

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